This is indeed a very difficult and personal decision!
The immediate reaction of may women is: "Take them both off!" because they want to lower the risk of ever having to deal with breast cancer again.
Others, and perhaps esp. those for whom breast stimulation and sensation plays an important role in their enjoyment of sensual and sexual activities, prefer to retain the healthy breast.
Some additional factors that might be taken into consideration are: whether the type of invasive BC you have has an elevated risk for recurring in the contralateral breast; how aggressive the grade of your tumor is; and whether you are willing to maintain the ongoing close surveillance (mammos? MRIs? U/S? --difficult to say, since as I understand it, your invasive componet didn't show up until the path. from the lumpectomy came back?) that would likely be recommended for the healthy breast.
When I noticed that you hadn't had any replies to your request for imput on the issue, I wanted to make sure you know that others understand that this is by no means an easy decision... (You probably have already thought of all of this, but perhaps it will be helpful to others facing the same decision.)
I am glad you have a treatment team that you trust and have available an accomplished plastic surgeon for your reconstuction(s). If you haven't fully researched yet all of the types available, you might want to take a look at the excellent coverage of this subject by SueYoung55 in a couple of previous threads: